Barbituric acid derivatives stabilizers for emulsions sensitized with ethylene oxide condensate

ABSTRACT

This application describes a process for the production of a gelatino silver halide emulsion which comprises forming the emulsion by a technique including a step wherein the emulsion is sulfur sensitized, and adding to the emulsion (1) an ethylene oxide condensate in quantity sufficient to increase the speed of the emulsion and the contrast of images developed therein, and (2) at least 1 g. per gram mole of silver halide present, of a compound of the general formula:   WHEREIN R1 is an aryl group and R2 is a lower alkyl group.

United States Patent Inventor Henry Walter Wood Ilford, England Appl. No. 702,543

Filed Feb. 2, 1968 Patented Nov. 2, 1971 Assignee Iltord Limited lllord, England Priority Feb. 13, 1967 Great Britain 6,830/67 BARBITURIC ACID DERIVATIVES STABILIZERS FOR EMULSIONS SENSITIZED WITII ETI-IYLENE OXIDE CONDENSATE 6 Claims, No Drawings U.S. Cl 96/94, 96/107, 96/109 Int. Cl G03c 1/02 Field of Search 96/94, 109, 107

References Cited UNITED STATES PATENTS 5/1912 l-loerlein 260/257 2,716,062 8/1955 Carrolletal 3,155,506 11/1964 Blake Primary E.raminerNorman G. Torchin Assistant ExaminerWon H. Louie, Jr. Attorney-Cushman, Darby and Cushman wherein R, is an aryl group and R, is a lower alkyl group.

EMULSIONS SENSlTlZED WITH ETHYLENE OXID CONDENSATE This invention relates to photographic materials and more particularly to the production of photographic gelatino silver halide emulsions. It is of particular significance in the production of emulsions designed to record X-radiation and will be described with particular reference thereto.

It is known that the sensitivity of a photographic gelatino silver halide emulsion may be increased by the addition to the emulsion of a nonionic wetting agent which is an ethylene oxide condensate or polyethylene oxide derivative. Besides modifying the physical character of coated layers of such emulsions the ethylene oxide compounds increase both the speed of the emulsions and the contrast of the developed images, and this may be due to acceleration of development.

When such ethylene oxide compounds are added to emulsions of the type generally prepared for use in X-radiography, these advantages are to some extent obtained, but the tendency of such additives to increase the fog density of the emulsion, especially after incubation, is found to be severe.

Various attempts have been made to reduce the fog level which arises from the use of ethylene oxide compounds by the addition of so-called antifogging agents. The bulk of those tested, however, have been found to be insufficiently effective.

It is the object of the present invention to provide a process for the production of silver halide emulsions so sensitized in which the fog level on development is reduced.

According to the present invention there is provided a process for the production of a gelatino silver halide emulsion which comprises forming the emulsion by a technique including a stepwherein the emulsion is sulfur sensitized, and adding to the emulsion (1) an ethylene oxide condensate in quantity sufficient to increase the speed of the emulsion and the contrast of images developed therein, and (2) at least 1 g. per gram mole of silverhalide present, of a compound of the general formula 1,--

wherein R, is an aryl group and R, is a lower alkyl group.

By lower alkyl is meant an alkyl group containing up to six carbon atoms.

The preferred compound of formula I is phenobarbitone wherein R, is phenyl and R, is ethyl.

The compounds are preferably. added to the emulsion as aqueous solutions, to which end an equivalent of an alkali hydroxide is used. Alternatively, the compounds may be used in the form of their soluble sodium salts. Optionally, an equivalent of an acid, such as HCl may also be added to maintain the pH of the emulsion at its original level.

Any of the ethylene oxide condensates and derivatives known from the literature to have a sensitizing effect on photographic silver halide emulsions may be employed. Preferred compounds are ethylene oxide homopolymers which are marketed under the trade name Carbowax and having relatively high molecular weights, e.g. 4,000 or more. However, derivatives such as the aromatic and alkyl ethers thereof, e.g. the commercial product Texofor F.60, are also of especial value. (The word Texofor is a Registered Trade Mark).

The quantity used will, of course, vary with the effect desired, but generally may be up to 20 grams of the condensate per gram mole of silver halide in the emulsion, e.g. 1 to 20 grams.

The quantity of the additive of the general formula given above will also vary with the circumstances, but will be at least 'iiiai'rarimlfgiveii'aba'v may be added to the emulsion at EXAMPLE A gelatino silver iodobromide emulsion was prepared in a manner conventional for emulsions to be used for X-radiography. The emulsion which was not color sensitized, contained 200 g. of gelatin per gram mol of silver halide and was sensitized by means of sulfur compounds and gold salts in manner known per se. The emulsion was divided into three parts:

1. No further addition was made.

2. Polyethylene oxide of molecular weight 6000 was added at the rate of 2 g. per gram mol of silver halide.

3. The same addition was made as for (2), and in addition there was added 10 g. of the sodium salt of the phenobarbitone per gram mole of silver halide, and an equivalent amount of hydrochloric acid.

The three emulsions were coated on film and exposed. They were then developed in a Phenidone based developer suitable for X-ray films. The following results were obtained:

(Incubation 7 days at F., 66 percent R.H.

it will be noted that the inclusion of the polyethylene oxide afforded an increase in speed but an unacceptable increase in fog. Thisfog was reduced by the addition of the phenobarbitone almost to the level of the control emulsion.

(Phenidone is a Registered Trade Mark of llford Limited).

1 claim as my invention:

1. in a process for the production of a gelatino silver halide emulsion which comprises forming the emulsion by a technique including a step wherein the emulsion is sulfur sensitized, and adding to the emulsion an ethylene oxide condensate sensitizer to increase the speed of the emulsion and the contrast of images developed therein, the improvement consisting of adding to the emulsion at least 1 g. per gram mole of silver halide present, of a compound of the formula:

Bi CO-NH wherein R, is an aryl group and R, is a lower alkyl group.

2. A process according to claim 1 wherein in the compound of the formula defined therein R, is phenyl and R is ethyl.

3. A process according to claim 1 wherein the compound of the formula defined therein is added to the emulsion as an aqueous alkaline solution.

5. A sulfur-sensitized gelatino silver halide emulsion sensitized with an ethylene oxide condensate to increase the speed of the emulsion and the contrast of images developed therein, said emulsion including at least 1 g. per gram mole of silver halide present, ofa compound of the formula:

7 R|\ /CNH ls an a ryl groep and R; is a lower alkyl group.

C CO 6. The emulsion of claim wherein R is phenyl and R, is ethyl.

R, CO-NH i i w n- 

2. A process according to claim 1 wherein in the compound of the formula defined therein R1 is phenyl and R2 is ethyl.
 3. A process according to claim 1 wherein the compound of the formula defined therein is added to the emulsion as an aqueous alkaline solution.
 4. A process according to claim 1 wherein both the ethylene oxide condensate and the compound of the formula defined in claim 1 are added after the emulsion has been sulfur sensitized.
 5. A sulfur-sensitized gelatino silver halide emulsion sensitized with an ethylene oxide condensate to increase the speed of the emulsion and the contrast of images developed therein, said emulsion including at least 1 g. per gram mole of silver halide present, of a compound of the formula:
 6. The emulsion of claim 5 wherein R1 is phenyl and R2 is ethyl. 